of stockholm



mus Sept. 22, 1931 I UNITED STATES PATENT orrlcs GUSTAF HAGLUND, OISTOCKHOLM, SWEDEN, ASSIGNOR '10' PATENTAKTIEBOLAGET GBbNDAL-BAMEN, OFSTOCKHOLI, SWEDEN,,A LIMITEDQOMPANY CELLULOSE COOKING Io Drawing.Original No. 1,791,476, dated February 3, 1981, Serial No. 432,564,filed March 1, 1880,1111! in Sweden April 10, 1929. Application forreissue filed June 8, 1931. Serial No. 542,688.

In the cooking of cellulose it has been suggested to add waste liquorfrom a prior coo ing operation to the fresh cooking liquor to be used,for ,the purpose of obtaining a re,-

;, sultant waste liquor containing a high con centration of organicmatter. Likewise, in

stead of utilizing waste liquor from a prior cooking operation, thewaste liquor from a cooking apparatus in operation may be em P e a ereresort is had to the use of waste liquor in such a manner however,undesirable effects occur in the cooking as compared with the ordinaryuse of a water solution of the cooking medium, without the addition ofwaste liquor. When waste liquor is employed as noted, the cookingprocess proceeds more .slowly, and the product readil tends to assume adark color and also to ome weak- :0 ened as a result of the extension ofthe cookin period. I

he present invention has for its object to overcome these disadvantageswhether the fresh cooking liquor is mixed with cooking liquor fromprevious cookings or with liquor from a cooking operation in action.According to my invention, prior to the cooking operation the rawmaterial, for example wood chips, is first caused to absorb the freshcooking liquor prepared in the usual manner with water, and thereafterwaste liquor is added, obtained either from a prior. cooking operation,or from a cooking apparatus the contents of which are in the process ofcooking. An illustrative procedure for can ing out the process of myinvention is as f0 lows: A fresh cooking liquor, which has notpreviously been used for cooking and which ma or may not contain gases,1s fed into a coo g 40 apparatus containing the wooden chips or otherraw material. The remaining unabsorbed liquor may then be withdrawn tothe extent necessary to accommodate the cooking liquor to besubsequent]; added. Therea after the apparatus is fills with a cookingliquor consistin of a mixture of the same fresh liquor as t at which hasbeen absorbed and a waste liquor from a previous or concurrent pulpcooking operation. The cooking operation in the apparatus thus chargedis thereupon be un and proceeded with to the degree desired.

This preliminary soaking will not occasion any loss of time as comparedwith the usual operation, because under all circumstances the chipsrequire time for the absorption of the cooking liquor. The processrequires however, an increased pumping action, and, for effecting arapid penetration of the unmixed cooking liquor into the chips, the

cooking apparatus 'is preferably completely filled with the fresh liquorin the preliminary step. The pumping means are so arranged that theliquor is introduced into the cooking apparatus under pressure in orderto facilitate the saturation of the chips and thereby shorten the timefor the absorption.

This saturation of the chips with the fresh cooking liquor prior to thecooking operation, ma of course, be conducted outside of the cob 'ngvessel or apparatus which is to be used, and the saturated chipsthereafter transferred to said apparatus, the apparatus filled withfresh cooking liquor mixed with waste liquor from the sources noted, andthe cooking operation proceeded with.

The impregnation of the chips with the fresh cooking liquor before thecookin process proper, as noted, is desirable in eacfi cooking ofcellulose and should be brought about as substantially and rapidly aspossible, for which purpose the use of pressure in the preliminarysoaking is highly desirable in cooking operations conducted as atpresent. This. preliminary soaking of the chips with fresh cookingliquor before the cooking operation and the subsequent cookin with amixed cooking liquor as described, 1s of like advantage in otherprocesses of cellulose cooking, for instance in alkaline cookingoperations, although the beneficial efl'ect is less marked than'in theproduction of eulphitecellulose. v 7

Having now particularly described the I nature my invention and themanner of its operation, what I claim is:

1. In the cooking of cellulose, for example sulphite cellulose, theimproved process of producing waste liquor containi a high percentage oforganic matter which comprises, impre atlng the raw material, for

' example woo chips, with a cooking liquor produced in the usual mannerwithout the addition thereto of waste'liquor, and then 1 conducting thecooking operation In the presence of waste liquor. i

2. A process as defined in claim 1 characterized m that the preliminaryimpregnation of the raw material with the usual cooking liquor iscarried out under pressure for the purpose of facilitatin theimpregnation.

. 3. In the cooking 0 cellulose, for example sulphite-cellulose, theimproved process of producing waste liquor containing a high percentageof organic matter whlch comprises, soaking the raw material, foreizample wood chips, in a cooking liquor reduced in the usual mannerwithout the ad ition thereto of waste liquor, removing part of thecooking liquor in which the raw material has been soaked, and thenconducting the cooking operation with the usual cooking liquor mixed 7with waste liquor froma previous cooking or from a cooking ap aratus inoperation. 86 .4. A process as de ed in claim 3 characterized 1n thatthe preliminary-soaking of the raw material with the usual coo liquor iscarried out under pressure for the purpose of facilitating thesoaking.40 In testimony whereof I aflix my si ature. GUSTAF HAGL NDg

